AP Biology :7.5 Hardy-Weinberg Equilibrium- Exam Style questions with Answer- FRQ

Question

Some people have the ability to taste a bitter chemical called phenylthiocarbamide (PTC). The ability to taste PTC is due to the presence of at least one dominant allele for the PTC taste gene.
The incidence of nontasters in North America is approximately 45%.

Assuming the population is in Hardy-Weinberg equilibrium, what percent of the North American population is homozygous dominant for the ability to taste PTC? Provide your answer as a number between 0 and 1 to the nearest hundredth.

▶️Answer/Explanation

Any value from 0.09 to 0.11, inclusive, or Any value from 9/100 to 11/100, inclusive

Question

ABO blood type in humans is determined bythree alleles of a single gene:\( I^A\), :\( I^B\), and i. The :\( I^A\)and :\( I^B\) alleles are codominant, and both alleles are completely dominant to the i allele. Shown in the table are the approximate genotype frequencies of ABO blood types for a large human population.

The Hardy-Weinberg principle can be applied to a genetic locus with three alleles by using the following equations.

\(p^2+ q^2+ r^2+ 2pq + 2pr + 2qr = 1\)

p + q + r = 1

Assuming that the population is in Hardy- Weinberg equilibrium with respect to blood type, what is the frequency of the i allele? Give your answer to two decimal places.

▶️Answer/Explanation

Ans:0.67 through 0.68

Question.

In a population of certain frogs in which the allele for brown skin is dominant to the allele for green skin, a drought leads to selection against green-skinned frogs. When the drought ends, 12 percent of the remaining frogs exhibit the green-skin phenotype.

If the population is now in Hardy-Weinberg equilibrium, what will be the frequency of the green-skin allele in the next generation? Provide your answer to the nearest hundredth.

▶️Answer/Explanation

Ans:0.34–0.35

The correct answer for the frequency of the green allele is 0.34–0.35. After the drought, the frequency of the recessive phenotype, q2 , was 0.12. Since the population is now in Hardy-Weinberg equilibrium, the frequency of alleles will not change, so q is the square root of 0.12, or 0.35.

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